Orthodontics Flashcards
1
Q
URA designs for:
- Retract canines and reduce overbite
- Retract and distalise canines
- Anterior crossbite
- Posterior crossbite/expand upper arch
- Reduce OJ/continue to reduce OB
A
- Palatal fingersprings and guards (0.5mm HSSW)
16+26 Adams clasps, 11+21 Southend clasp (0.7mm HSSW) - Buccal canine retractors (0.5mm HSSW) and 0.5mm ID tubing
16+26 Adams clasps, 11+21 Southend clasp (0.7mm HSSW)
FABP - Z-spring (0.5mm HSSW)
14+24+16+26 Adams clasps (0.7mm HSSW)
PBP - Midline palatal screw
14+24+16+26 Adams clasps (0.7mm HSSW)
Reciprocal anchorage
PBP - Roberts retractors (0.5mm HSSW) and 0.5mm ID tubing
13+23 mesial stops (0.6mm HSSW)
16+26 Adams clasps
FABP
2
Q
Orthodontics Lab
- 5 URA dislodging forces
- How HSSW made
- Bauschinger effect
- 4 ways steel fractures
- 3 types of appliances and how they work
- ARAB (definitions, HSSW diameter of each type of component, B function, why self-cure)
A
- Gravity, muscles (tongue), active components, speech, mastication
- By drawing cold state metal through a series of successively smaller diameter dies. Also causes work hardening, increasing springiness
- Unwinding spring/coil peat elastic limit causes a permanent change in material shape
- Overwork, mechanical abrasion/crushed/marked, fatigue, weld decay
- Removable - tipping
Functional - influences orofacial muscles and dentoalveolar development
Fixed - rotation, torque, bodily movement - Aim
Active components - 0.5mm HSSW. Any component that uses force to move a tooth/teeth. 1-2 at a time
Retentive - 0.7mm HSSW. Resistance to displacement forces
Anchorage - resistance to unwanted tooth movements
Base-plate - self-cure PMMA (quicker, cheaper, sufficient mechanical properties). Provides anchorage, connector, retention through adhesion-cohesion
3
Q
URA fitting
- URA first time fitting what to check
- URA fitting patient instructions
A
- Check for right patient, check design matches prescription, check for sharp areas, check for pre-existing damage, try in and check for trauma/blanching, check posterior retention (flush flyover, then check arrowhead engages undercuts), check anterior retention, activate appliance for 1mm movement per month (uncoil spring coils), demonstrate to patient how to get it in and out, get patient to demonstrate putting in and taking out, review every 4-6 weeks to reactivate active components
- URA is big and bulky but will get used to it, might affect speech so practice reading out loud for speech, excess salivation but only for first 24 hours, might be achy and mild discomfort – means it is working, avoid hard and sticky foods, be careful with hot foods and hot drinks, wear all the time, take out if doing contact/active sports, take out and clean after every meal, poorer compliance = longer treatment, emergency contacts – if something breaks off, get in touch
4
Q
Ortho treatment
- 3 aims
- 3 indications
- 3 contraindications
- 3 benefits
- 3 risks
- 3 limitations
A
- Stable, functional, aesthetic occlusion
- Increased risk of trauma/disease, impaired oral function, unaesthetic/psychological
- Uncontrolled epilepsy, poorly controlled diabetes, poor attendance/motivation, poor OH
- Reduces risk of trauma/disease, improves function, aesthetics, dental health
- Decalcification, relapse, root resorption
- Teeth only stable in neutral zone (may relapse), no/minimal effect on skeletal patterns, movement limited by shape and size of alveolar process
5
Q
Occlusion
- Define ideal occlusion
- Define normal occlusion
- Define malocclusion
- What are the ideal occlusal features (6 keys)
A
- Gold standard by which occlusal irregularities and treatment may be judged. Anatomically perfect, class I relationships
- Minor deviations from ideal that do not constitute functional/aesthetic problem
- More significant deviations from ideal that may be considered functionally/aesthetically unsatisfactory and may require treatment
- Correct molar relationship, correct crown angulation, correct crown inclination, absence of/no rotations, tight proximal contacts (no spaces), flat occlusal plane
6
Q
Classification definitions
- BSI
- Angle’s
- Canine
A
- Class I - lower incisor edges occlude with/lie immediately behind cingulum plateau of upper central incisors
Class II - lower incisor edges lie posterior to cingulum plateau of upper incisors
Class II div. 1 - upper incisors are proclined/of average inclination. Increase in overjet
Class II div. 2 - upper central incisors are retroclined. Overjet usually minimal/may be increased
Class III - lower incisor edges lie anterior to cingulum plateau of upper incisors. Overjet reduced/reversed
2. Class I/neutrocclusion - MB cusp of U6 occludes with buccal groove of L6 Class II/distocclusion - MB cusp of L6 occludes distal to class I position. Post-normal relationship Class III/mesiocclusion - MB cusp of L6 occludes mesial to class I position. Pre-normal relationship
- Class I - U3 mesial slope occludes with L3 distal slope. U3 cusp occludes between L3/4 contact/with embrasure between L3/4
Class II - U3 occludes mesial to L3/4 embrasure
Class III - U3 occludes distal to L3/4 embrasure
7
Q
- 2 types of crossbite
- Define overjet
- Define overbite
A
- Buccal, lingual. Described lower to upper (lingual crossbite normal)
- Extent of horizontal (AP) overlap of upper central incisors over lower central incisors
- Extent of vertical overlap of upper central incisors over lower central incisors. Normal if uppers cover 1/3 or more of lower when in occlusion
8
Q
Skeletal base assessment
- 2 methods for AP
- 2 methods for vertical
- One method for transverse
- Skeletal classification (AP classification)
- Class I, II, III cephalometrics (SNA, SNB, ANB – moderate, mild, severe)
- Features of long/short face (AFH, FMPA)
A
- Visual, palpate skeletal bases, ANB (cephalometrics)
- FMPA, anterior face height
- Mid-sagittal reference line
- Class I - maxilla 2-3mm in front of mandible
Class II - maxilla >3mm in front of mandible
Class II - maxilla <2mm/behind mandible - Class I - SNA - 81±3, SNB 78±3, ANB 3±2, FMPA 27±4
Class II - SNA increased/average, SNB reduced, ANB >5 (4-6 mild, 6-8 moderate, >8 severe)
Class III - SNA reduced, SNB average/increased, ANB<1 (0-2 mild, 0-(-3) moderate, 55% of AFH, FMPA >31, anterior open bite tendency
Short face type - LAFH <55% of AFH, FMPA <23, deep overbite tendency
9
Q
Local malocclusion
- Define
- 4 reasons (4 reasons of tooth number)
- 4 types of supernumeraries
A
- More significant deviations from ideal that may be considered functionally/aesthetically unsatisfactory and may require treatment, confined to one/a few teeth in one arch
- Supernumerary, hypodontia, retained primary tooth, early loss of permanent tooth, micro/macrodontia
- Odontome (complex, compound), supplemental, tuberculate, conical
10
Q
Tooth movement
- 3 theories (describe one)
- 6 types (and associated pressure (g) with each)
- Pathophysiology of light forces associated with tooth movement
- Pathophysiology of moderate forces associated with tooth movement
- Pathophysiology of excessive forces associated with tooth movement
- 4 factors affecting response to orthodontic force
A
- Differential pressure theory - intermittent forces lead to areas of pressure and tension, cause bone resorption (pressure side) and bone deposition (tension side), causing teeth to be moved in the direction the force is pressing in
Mechano-chemical theory (pressure causes chemical release causing resorption/deposition)
Piezo-electric theory ((pressure causes electric current generation causing resorption/deposition) - Tipping (35-60g), bodily movement (150-200g), intrusion (10-20g), extrusion (35-60g), rotation (35-60g), torque (50-100g)
- PDL hyperaemia, osteoclasts and osteoblasts appear, resorption of lamina dura from pressure side, apposition of osteoid on tension side, remodelling of socket, PDL fibres reorganise
- Occlusion of PDL vessels on pressure side and PDL vessel hyperaemia on tension side, pressure side hylinisation (cell-free area), period of stasis, undermining resorption (increased endosteal vascularity), relatively rapid movement of tooth with bone deposition on tension side (mobility), healing of PDL – reorganisation and remodelling
- Necrosis, undermining resorption, root surface resorption, pain, permanent change
- Magnitude, duration, age, anatomy
11
Q
Facial growth
- When IUL
- 2 types of skull
- How neurocranium grows
- What is unique about jaws
- Mandible units and why they develop
- Growth of skull when born (vault and base)
- Sites of secondary cartilage formation in mandible
A
- 7-8wks IUL
- Viscerocranium (face), neurocranium (vault and base)
- Intramembranous ossification - vault
Endochondral ossification - base - Develop intramembranously (intramembranous ossification) but adjacent to/preceded by cartilaginous skeleton (nasal capsule and Meckel’s cartilage)
- Condylar, coronoid (in response to temporalis), angular (in response to masseter and medial pterygoid), alveolar (only if teeth present), body (in response to IAN)
- Vault - at fontanelles/sutures (anterior closes at 2, posterior closes at 1). Growth at sutures until 7 and then external surface deposition/internal surface resorption
Base - cartilaginous growth centres between sphenoid and occipital bones and in nasal septum - Condylar, coronoid, symphysis
12
Q
Syndromes
- Difference between primary and secondary abnormality
- 4 types of syndrome (define)
- 3 types of embryonic stage syndromes (2 features of each)
- 3 syndromes associated with skull growth (3 features of each)
A
- Primary - anomaly in development causes structural defect
Secondary - external influence interrupts/stops normal development - Deformation - anomaly due to external mechanical effect on existing structure
Agenesis - failure to form/develop (absent)
Sequence - single factor cause numerous secondary effects
Syndrome - group of anomalies with common origin - Foetal alcohol syndrome - small head, cognitive impairment, short nose
Hemifacia microsomia - spectrum of facial asymmetry
Treacher Collins - mandibulofacial dysostosis. Hypoplatic/missing zygomatic arch, mandible
Cleft lip and palate - crowding, hypo plasticteeth, ‘nick’ out of lip, caries
4. Achondroplasia - problems with endocondral ossification. Stunted growth, long bones develop normally (large vault), BoS defects Crouzon's - early closure of coronal and lamboid sutures. Proptosis, prominent nose, class III Apert's - early closure of almost all cranial sutures. Parrot beak, acrosyndactyly, class III, AOB, CLP (30%)
13
Q
Post-natal growth
- 3 places where it occurs
- 2 effects of adverse growth rotations
A
- Cranial sutures, base of skull synchondrosis, surface deposition beneath periosteum
- Forward - short face
Down and backward - long face
14
Q
Interceptive ortho
- Define
- Dental features at birth
- Primary eruption
- Primary spacing/permanent crowding relationship
- Permanent dentition eruption
- Leeway space
- Balancing/compensating extractions - define and when to use
A
- Any procedure that will eliminate/reduce severity of a developing malocclusion (utilisation of eruption and growth)
- Class II, AOB, gum pads (upper rounded, lower U)
- 6mths-3yrs - a-b-d-c-e
- No spacing = 66% crowding risk
<3mm spacing = 50% crowding risk
3-6mm spacing = 20% crowding risk
>6mm spacing = no crowding risk - Early - 6s (6), 1s (7), 2s (8)
Late - 4s, (10), 3s and 5s (11-12), 7s (12-13) - Difference between c, d, e and 3, 4, 5. Maxilla = 1.5mm, mandible = 2.5mm
- Balancing - extraction of same tooth on opposite side of arch to minimise centre-line shift. Uc’s
Compensating - extraction of opposing tooth in opposite quadrant to minimise occlusal interference and prevent over-eruption. L6’s
15
Q
Interceptive ortho 2
- Management of early loss of primary teeth
- Management of early loss of 6s (and best time to lose 6s)
- Treatment of developing crossbites (anterior and posterior)
- Management of unerupted permanent central incisor
- Management of ectopic 6
- Management of retained primary tooth
- What is an infra-occlude tooth and how is it managed
A
- A/B - monitor. C - balance. D - consider balancing. E - monitor
- If L6, compensate. Best time when 7s bifurcation forming, 5s and 8s present, moderate lower crowding
- Anterior - treat early (when 2s erupt) with URA and z-spring
Posterior - overcorrect with URA and midline screw - Observe (1.5yrs), create space, remove supernumerary/deciduous tooth, exposure and bond
- Extract e, distalise 6
- If successor present - usually exfoliates/extract 1yr later
If successor absent - extract early (space closes) or retain as long as possible - Submerging - ankylosed primary tooth with occlusal surface lower than other teeth
If successor present - usually exfoliates/extract 1yr later
If successor absent - extract when 1mm of crown left showing above gingival margin
